GREEN-STONE. 



This rock, with a view to the periods of its formation, 

 i" divided into primitive, tranfition, and fletz grecn-ftone. 



The /iiimilive greenllone is gcnei-ally diftinguifhahlc from 

 the others bv its highly cryilalline ftriicturc. The liorn- 

 blende, in which a tendency to cr\llalhzatJon is ahr.oil 

 always obfervable, generally conilitutes the predominant in- 

 gredient ; but fomctimes this is only apparently fo, the 

 feldfpar being not leldom ftained by it in fucli a manner, 

 that it bears the greatell refeniblance to fniall laniinx of 

 hornblende. In tliis cafe the blow-pipe difcovers the illu- 

 fion bv melting the hornblende ; when the feldfpar recovers 

 lis ulual whitilh colour, and i» converted into a white glafs. 



AVerner fubdivides primitive green-flone into four varieties: 

 I. Common gri'en-Jlone, in which the two ingredients, mixed 

 in different proportions, form a granular mafs. 2. Por- 

 phyritic grecn-ftons, being tlic common variety, including large 

 ciyllals of feldfpar. 3. Great-Jloae porphyry, in which " the 

 granular batjs, whicli is with difficulty dillinguifliable, in- 

 cludes crvllals of feldfpar :'" and 4. Green porph\r-f, m which 

 " the granular nature of the bafis is no longer vilible to the 

 niked eye ; it appears uniform and il;ii]>le ; has a blaekiili 

 green or piftacliio green coloui', and includes cryllals of 

 r'jnipaft feldfpar." (Jamefon.) To tliefe are to be re- 

 ferred the porlido nero, and porfido verde antico of 

 Italian antiquaries, of which we (hall fav m.orc kerearei-. 

 The third and fourth of thefe varieties might, we tliink, be 

 fafely united ; at leail llie deiinition given of them does not 

 indicate any diflerence, except in the ihade of green. 



This old green-ftcne appears fometimes ilratified. Gneifs 

 is the rock in which the diiterent varieties tirft appear ; the 

 next rock in which thev occur is mica-flate, but the beds of 

 sreen-llonc in either of them are icantv and inconfiderahle ; 

 t!iey arc obferved more numerous and of greater extent in 

 cky flate in Scotland. According to Mr. .lamelon, the clay- 

 (late and mica-flate, that form a great portion of the country 

 extending from Loch Lomond, by Callander, Comrie, and 

 Hunkeld, contain numerous beds of greeu-ilone ; and there, 

 v.e are informed by this geognofian, as in all other countries, 

 the clav Hate centains more numerous and larger beds than 

 the mica llate. 



There is a vaft number of varieties of primitive grecn-ftone 

 in- Bohemia ; thus it is found in the Saatz diilrict of that 

 country, where it reits chiefly on gneifs. It occurs there 

 alio with quartz as a conftituent part. The varieties mencioncd 

 by Reufs, as being found there within a narrow comjiafs, 

 afie, I. A fniall grained mixture of velvet black hornblende, 

 which exhibits a tendency to a priimatic cryftalline torni, 

 with yellowifli while feldlpar, and greyilh-whit-e and Inioke 

 grey quartz. The hornblende is she predominant part ; the 

 quartz is here and there entirely wanting ; the mixture 

 pretty uniformly granular. 2. A variety in which the horn- 

 blende is feen in gi-oups, dilHncf from tliole of the feldfpar 

 aud q.iartz ; fo that the whole forms an afTembhijre of bhick 

 and yellowilh-uliite fpots. 3. A variety in which the horn- 

 blende is fo prevalent, that feldfpar and quartz can wiili 

 dvfHculty be diilingnilhed by the magnifying glais, which 

 difcovers ihefe ingredients collected into fmu 1 fpots and 

 flrip-s ; it contains alfo here and there fon-.e fcales of mica. 

 4. Var. in which the hornbk-nde is fecn partly maflivc, in 

 fpots, ilripes uniformly bleuiied with the leldipar ai:d 

 quartz ; partly in fn.all circular cryilals that are divergingly 

 a'igregated, or crofs each other in liil directions ; feklipar 

 tile and brownifii-red ; quartz only I'.ere and there in fmoke 

 grey grainSi. 5. Var. in which the hornblende Ihuws a ilrong 

 tendency to crylfallization, and is much accumulated in lome 

 places; though, generally fpeaking, its proportion to the mix- 

 ture of yellowilhrwhite and rcddi(h-grey feldfpar and greyilh- 



white quartz, is but fmall : it contains larger and more nu- 

 merous fcales of fdvery and )ellowiih-whitc mi<ra. 6. Var. 

 in which the texture becomes more tiiick-flakv ; the fmokc- 

 grey quartz becomes predominant, the yellow'ilh-white feld- 

 (par difappears almoil entirely, and the hornblende is only 

 thickly diffeminated. 7. Var. in which the vellowifh-whife 

 and rcddifh-grey feldfpar i)redominates over the hornblend' , 

 winch is feen partly maflivc and in hne granular concretion?, 

 partly in infidated and difperfed miimte fix-fided prifms, 

 imbedded in tlie feldfpar ; while the quartz is cntirelv want- 

 ing. It is remarkable that in this diflrict the p'rim.itivf 

 gr-en-rtone is feen, by flow gradation, to pafs over into' 

 jierfecl gneifs. The more it approaches the latter, the more 

 the granular texture becomes indidinct ; the rock adopts a 

 thick llaty texture, the hornblende is feen more and mon- 

 to dimmifh, while the mica increafes both in quantity and 

 li/e, until ported gneifs Hands confefled as the conftituent 

 rock. 



This rock is common alfo in many other parts of Europe ; 

 but the accounts we pofli-fs of the green-ftone of feveral 

 countries is t o imperfect to enable us lo determine how much 

 of it may be conhdercd as primitire. 



The traajhion grefn-Jlone is not eaiily difcrimiiiated in hand- 

 fpeciniens. It is cliaracierized by Mr. .lamefon as bein'r 

 " a fiiie granular mixture of hornblende and feldfj)ar ; and 

 fometimes the mixture is fo intimate, that the conftiti:ent 

 parts are not to be dillinguiflied. Quartz fometimes tra- 

 vcrfcs it in the form of veins, or is ditieminated throu'rh it ; 

 a character whicli diflinguiihes it from fl^tz green-ftonc, 

 which rarely contains quartz. Sometimes it occurs in glo- 

 bular diftinct concretions, and thefe again conlift of curved 

 lamellar concretions, forming the globular rock (ku"-elfe!s> 

 of Voigtland. Sometimes it is penetrated with reddifli' 

 brown oxyd of iron, which, combined with the d.irk-brown 

 hornblende, gives the rock a liver-brown colour ; hence it is 

 denominated in Voigtland, where it occurs, leber-fels, or 

 liver rock. Beds of it occur in the upper part of Dum- 

 friesfliire, in the Hartz, Bohemia, &c." 



Flflz-green-Jlnnf. Prof. Jamefon, in his " Mincralogical" 

 Defcription of Dumfriesftiire," has given a fliort account of 

 the occurrence of green-ftone in the independent coal-forma- 

 tion ; and Mr. Fliirl has difcovered beds of amygdaloid in 

 the firft or oldeft fletz-linie-ftone ; whence the former autiior 

 confiders himfelf entitled to introduce what he terms the 

 f.-t'z.-trap, wiiich is diilinct f om tiie ftill newer formation 

 called the ne--Mji fitz-trap by \\'erner. In the independent 

 coal formation it occurs in beds from one foot to many 

 fathoms in liiickncfs ; it contains imhedded olivine anil 

 augite, and is traverfed bv numerous veins of cale-fpar ; it- 

 often alio con' ains drufy cavities, which arc lined with calc-- 

 fpar, quartz, baryt:s, cubicite nuid prchnite ; and the ca- 

 vities arc iomctimis filled with water. 



The green-ftone <:f Werner's luxvrO fietz-lr.ip formnliin 

 is, upon the w!iole, ('.illii;^-;!ifli:.ble froni the older formation,, 

 by its- ftriicture being of a leis cry(!ailir.e appearance, and 

 by i:s diftnict coticretions appro:iciiing more to the coarfe 

 granular. •' Its colour ufual y inclines more oriefs to green. 

 Certain varieties are redviifh, :nid thefe are denominated 

 fi.Miitic green-ftone. \\iien frifti and rather large ■■'ranulr.r, . 

 it ufiially exhibits a fmiple ftrutture ; whtii, on l!ie con- 

 tr; ry, it is dilintegrated, and fm.nller granular, it occurs in 

 globular, and thei'.- again in curved !a"icl!ar dilind concre- 

 tions. Certain, varieties approaeii to w acke, and thefe are 

 ufirally velicular,. and form a kind of amygdaloid. It is 

 fometim.s very diftindly ftratified, and frequently tcciirs in 

 veins." .lamefon. 



The ufes lo which the common grccn-llone is applied are ■ 



noli 



